Equipment running at higher rpms, such as small electric motors, usually requires lower oil viscosity. If a grease is too thick or too high in oil viscosity for the bearing to properly function, fluid friction develops within the bearing. The resulting buildup of friction and pressure makes the bearings overheat, which causes rapid oxidation of the grease and can lead to premature bearing failure.

Understanding the need and the methods for appropriate grease selection will go a long way toward improving lubrication programs and the reliability of lubricated machinery. When in doubt, consult your lubricant supplier who will have a wealth of knowledge to help you choose the correct greases for your specific equipment.

Not enough lubrication
A second and much more common cause of grease-related equipment failures is a lack of lubrication from improper or poor maintenance practices. Under-greasing creates extreme heat caused by friction buildup and will eventually lead to high levels of metal-to-metal contact between bearing components – causing equipment failure or breakdown. Equipment failure, downtime, and lost productivity can be costly byproducts of under-greasing or failing to properly lubricate components. It also shortens the grease life considerably.

Following a company’s reorganization, a customer approached our lubrication engineer about bearing failures on a specific portion of his plant, asking how the failures could be related to improper greasing. The customer suspected that the wrong grease was being used.

Research revealed that, during the reorganization, an employee had been laid off – an employee who conducted and maintained regular grease re-lubrication intervals at this plant on a monthly basis. After the layoff, the bearings had gone well over six months without any grease maintenance.

The lack of adequate lubrication, coupled with the extreme conditions experienced at this plant, began to cause bearing failures. Without proper lubrication of the bearings, equipment can be shut down and production ceased. Lubrication and maintenance is cheap compared to the alternative – a plant that is not running.

This situation exemplifies the critical role grease plays in equipment reliability and reinforces the value of a regular program to monitor lubricant applications. Maintaining the proper amount of grease is crucial. Be sure bearings are properly greased during installation and re-grease the bearings at the appropriate intervals based on your particular equipment needs and operating parameters.

Too much lubrication
Over-greasing can be as bad as under-greasing. Over-pressurizing bearing seals by applying too much grease can lead to higher grease usage, overheating, and mechanical failures. If the bearing seal is damaged or blown out, equipment or bearing life can be shortened by more than 50 percent due to the introduction of external contaminants.